1. Field of the Invention
The present invention relates to an air bag apparatus of a vehicle, and more particularly to an air bag apparatus for a front passenger.
2. Description of the Related Art
An air bag apparatus for a front passenger of the motor vehicle Is structured such that an air bag is received in a folded state in an instrument panel positioned below of a front window panel. The air bag is structured such as to expand due to a gas injected out from an inflator at a time of collision, develop toward an inner side of a passenger""s room from an upper portion of the instrument panel and receive the passenger falling forward so as to protect the passenger.
A tether belt extending in a longitudinal direction from a gas introduction port of an air bag to a portion close to a rear end is provided in an inner portion of the air bag used in this kind of air bag apparatus, for example, as is known in Japanese Patent Application Laid-open No. 11-5505. The tether belt has a function of guiding a gas stream output from the gas introduction port to the rear end side of the air bag in an initial expanding state of the air bag, and a function of restricting a linear development of the air bag to an inner side of the passenger""s room and developing so as to extend in a vertical direction.
However, in the prior art mentioned above, the tether belt is long and the rear end of the tether belt is positioned in the passenger compartment disposed beyond the rear end of the instrument panel in the initial expanding state of the air bag. Accordingly, in the case of a normal state in which the front passenger existing in the front passenger""s seat is sufficiently apart from the instrument panel, the air bag in the initial expanding state expands upward and downward with being restricted to develop rearward by the tether belt before reaching to the passenger mentioned above, however, in the case that the passenger is much close to the instrument panel, the rear end of the air bag is brought into contact with the passenger before expanding upward and downward at a stage of the initial expansion, so that there is a risk that an excessive impact is applied to the passenger.
In order to prevent the excessive impact from being applied to the passenger in the latter state, it is necessary to provide with a rotating mechanism for changing a developing direction of the air bag and a sensor for detecting an approaching state that is out of usual position. Then, the structure is made such that a developing angle of the air bag is changed to a direction in which the excessive impact is not applied to the passenger, at a time of detecting the approaching state by the sensor, however, according to this countermeasure, a cost is significantly increased.
The present invention has been made in consideration of the prior art mentioned above, and an object of the present invention is to provide an air bag apparatus for a motor vehicle which can securely protect a passenger even in an approaching state without significantly increasing a cost.
According to a first technical aspect of the present invention, there is provided an air bag for a vehicle having a front portion including a gas introduction port introducing an inflation gas therethrough wherein the air bag is placed at a predetermined position of the vehicle interior with respect to the gas introduction port and develops rearward due to a motivation, a tether belt connecting the gas introduction port and a rear portion at an upper side of the air bag, wherein a rear end portion of the tether belt extending in an initial developing stage of the air bag toward a vertical surface passing a rear end of an instrument panel of the vehicle is positioned in the surface.
According to a second technical aspect of the present invention, a length of the tether belt is equal to or less than a horizontal distance between the gas introduction port and the vertical surface.
According to a third technical aspect of the present invention, a front end of the tether belt is connected to a rear edge of the gas introduction port.
According to a fourth technical aspect of the present invention, the rear end of the tether belt is connected to a portion forming an upper surface portion of the air bag.
According to a fifth technical aspect of the present invention, the tether belt is provided with a front side belt a front end of which is connected to the gas introduction port, and a rear side belt connected to another end of the front side belt and having a middle portion connected to an upper side of the air bag so as to constitute a patch portion having a predetermined area and two end portions both connected to another end of the front side belt.
According to a sixth technical aspect of the present invention, the tether belt is provided with a front side belt having two end portions and a middle portion of which is connected to the gas introduction port so as to constitute a patch portion having a predetermined area, and a rear side belt connected to another end of the front side belt and having a middle portion connected to an upper side of the air bag so as to constitute a patch portion and two end portions both connected to both ends of the front side belt. Accordingly, since the front side belt is also constituted by a two-sheet structure, a strength of the tether belt is improved, and the gas introduction port is reinforced by the patch portion of the front side belt.
According to a seventh technical aspect of the present invention, the air bag is formed in a bag shape by connecting a lower base fabric and an upper base fabric, the gas introduction port is provided in a front portion of the lower base fabric, one end of the tether belt is connected to the upper base fabric, the tether belt has one front side belt in which a front end of the lower base fabric is connected to the gas introduction port and a rear side belt a middle portion of which is connected to the upper base fabric so as to constitute a patch portion having a predetermined area, and both end portions of the rear side belt are connected to a rear end of the front side belt.